Phase I trial of the farnesyl transferase inhibitor R115777 in combination with capecitabine in patients with advanced, refractory malignancies. The primary objectives are: 1) to define the maximum tolerated dose (MTD) of the combination when administered orally BID for 14 days in a 21 day cycle, 2) to evaluate the pharmacokinetic profile of both agents, and 3) to determine the toxicity profile of the combination. Patients will be enrolled onto successively higher dose levels until an MTD is reached.